net: dsa: mv88e6xxx: fix unreleased fwnode_handle in setup_port()

'ports_fwnode' is initialized via device_get_named_child_node(), which
requires a call to fwnode_handle_put() when the variable is no longer
required to avoid leaking memory.

Add the missing fwnode_handle_put() after 'ports_fwnode' has been used
and is no longer required.

Fixes: 94a2a84f ("net: dsa: mv88e6xxx: Support LED control")
Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>